Hi....I have installed a cam into my 79 Z28.I was told that if i installed a cam with the lift under 460 lift it would run ok with the stock heads and intake and carb...well after i fired the car up it would not idle for nuthin...very lean..If you putt ur hand over the carb then it would idle..tryed to adjust the carb but it doesn't seem to help....the engine is a stock 350 . the only thing that was changed is the exhaust....stock manifolds but has 2 1/2 inch pipes with high flow convertors and flowmaster mufflers...can i jet the Quadrajet carb to work or do i have to replace it with an aftermarket carb?????

Oh....1 other thing in order ta get the car to run I drilled the primary jets out one size bigger.....after you drive the car you can smell the exhaust system...sulfer smell from the convertors... any help would be great thanks Cly

I would double check and make sure you didn't forget a vacuum line. From the sounds of it you very well could just have a vacuum leak. Double check your manifold bolts and all vacuum hoses and fittings. Just changing the cam should not have caused the problem you are experiencing.

Royce

Either you got a bad intake leak or you forgot a vacuum line like camaroman said. The vaccuum line for the auto transmission could have sliped off the modulator on the trans when you pushed it out of the way to put your intake on. It happened to me and it took me a while to find out thats what happened http://www.camaros.net/forum/smile.gif

I got a Lunati cam with .458 lift and 218 @ .050 and 284 adv. duration with stock heads, stock iron intake, and a 2 barrel carburator and I didn't have any problems.

Btw, new cats always stink like sulfur when they're new http://www.camaros.net/forum/smile.gif

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Chris Rose
1981 Camaro
355ci 2 barrel carb

How much did you drill out the pri. jets?. If you don't have a vacuum leak it should idle. I have a 79 Vette that has the same setup as yours and there is about a mile of vacuum line on the thing. Make sure they all are going to the correct place and are not leaking. Your carb has an adjustable power piston that can be used to make the part throttle run very well even with alot of cam which is unlike the earlier ones. Mine has 72 main jets in it and runs well but I did end up replacing just about all the vacuum lines before it would.

DRILLED the jets??????
What is this a joke thread????
You can't drill the jets withot screwing them up....they need to be honed to a very fine finish then put in a flow measuring machine to see were they rate at then they are labeled... The companies that make jets ..even with all the proper care in machining ..still have VERY poor process variation..ie.e they still have to measure each one before they are stamped at their ratting..and this is about 5% to 10% trolerances...
You need to buy various jet sizes and set it properly..
The idle has nothing to do with jets in the Q-Jet and shouldn't either..
If you are having idle problems with a big cam you may need to open up the idle tubes and or drill small holes in the throttle plates...
What size cam is this??
CHEERS
CHRIS

you really shouldn't have drilled out the jets, thats 99 out of a 100 a BIG no,no.but you could be the 1 that got it right.it sounds like a vacuum leak,but if the duration of the cam was much over 218@.050 then the carb will have to be recalibrated like stated before. hope you get it staightened out,... buy the way THE CARB SHOP sell Q-jet jets for about $2 a set.

Lots of info....thanks
I know i should not have drilled those jets out...But hey ya live and learn..The cam is not that big.. I was suprised that it ran the way it did when I finished it up...A friend of mine has the same car in a 350 borad 30 over with headers,preformer intake and holly 750 carb and it does gust fine...As far as the vacumn leak all the lines are on and in the proper place but I did not remove the oil fill cap to see if it is leaking internaly.That could be the case...The intake that is ont the Car is Chrome plated,and when i removed it I thought at first it was stuck,But it was just heavier than you know what....about 65 ta 70 pounds i would say.....So it is very possable that during the install the gaskets may have shifted......I will check into that and post what I find

Thanks alot guys Cly

Well I have searched all over for a vacumn leak and can't find any...I'm not to sure what to do now???????I'm lost...I dont know if a new intake and carb set up would correct this problem?Also I would like to keep the stock air cleaner assembly.......any other ideas???????????

Cly

Start the car and spray carb cleaner around the carb and intake gaskets. If the idle picks up, you have a leak.Don't spray it near the exhaust!!!!!!!! If you put your hand over the carb mouth and the car idles, it is sucking air somewhere else. The car should die when you do that.

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Bob
Garnet Red 69/SS396/TH400/355 Posi
94 HD Dyna Wideglide

did you do anything else to the carb like turn the power piston set screw(power valve)?

I did spray carb cleaner around to look for the leak but didn't find anything....and the jets are the only thing I messed with.I have had cams in other cars that ran ok with the Quadrajets??had a pontiac that had a cam in it with a little 2 bbl carb and it ran jets fine....I don't get it.....Does anyone know of anyone in the Indianapolis area that is good with carb's?????


Cly

get a "new set of jets,start around 72 or 74( order them or go to the junk yard), then let us know. or put the carb on a friends motor to see if its even the carb.that would be the best thing to do.those jets are REALLY a precise part. some of them are stepped and you could have caused them to flow LESS fuel even though you drilled them out.

Another way to find a vacuum leak is to pull the vac lines off one at a time and plug them temporarily. You found the culprit if the car suddenly idles better. You could also have a component at the end of a vacuum line that is leaking - like a power brake booster - even if the lines themselves are good.

BTW - I'd put in some new jets before trying anything else.

Ok I'll get some new jets and try those....You say I should start out with 73 or 74 size jets ????should I also change the metering rods ???? If so what size mettering rods


Cly

start with the jets first.metering rods are hard to come by(primary) unless the carb shop sells them,i've never asked. it wouldn't make a huge difference any way with the primary metering rod change on a Q-jet because only about 20%-30% if the air flow comes from primary side.

Borrow your friend's carburator for a test to see if the problem is even in the carburator. Then when you determine that it is not the carburator. Junk that boat anchor intake and go lay down the 100 bucks for a new Edelbrock. It sure sounds like you have a vacuum leak.

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67 Camaro, 355, Trick Flow G2 heads,RPM intake, XE274, TH350 with Hughes 3000, 4.10 posi

1979 stock carburetors are calibrated lean and need to be sent off to a professional to run right. Save time and money and go buy yourself an Edelbrock carburetor. Your car should purr like a kitten then

Try tipping the choke closed a bit when idling. If the engine "likes" this, you need to open up the idle feed restriction.
I like to check for vaccum leaks by using a water filled squirt bottle. Water is less mess.
Drilling the main jet most likely richened your cruse mixture and may melt your catylitic converter. That could be what you smell.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350
Can Am Vintage Racer

I think you've installed the cam in a retarded position. Check the lift vs crank position listed on the cam card

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Racer Ed

throw you carb in the trash can & bolt on a 750 holley double pumper, set the timing & be done with it. the smell is the converters to oxygen lean

[This message has been edited by mastertekh (edited 05-20-2001).]

[This message has been edited by mastertekh (edited 05-20-2001).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by mastertekh:
throw you carb in the trash can & bolt on a 750 holley double pumper, set the timing & be done with it. the smell is the converters to oxygen rich
[This message has been edited by mastertekh (edited 05-20-2001).]

[This message has been edited by mastertekh (edited 05-20-2001).]<HR></BLOCKQUOTE>

if your going to throw your q-jet in the trash i'll gladdly take it off your hands!!!
some people do this when they don't know how to tune them,they look very complex you know.

[This message has been edited by sldhd (edited 05-22-2001).]

Try this, remove the PCV valve from the valve cover and plug everything else that runs in or out of your valve covers. shoot carb cleaner (or better yet, use a propane enrichment tool) directly into the breather on the valve cover... this can hilight a vacuum leak under the intake, that is impossible to find by messing around on the top. This blew my mind when i was a kid (and we found a leak under a customer's intake) causing the car to run like stink

Ok guys......I have orderd jets from jegs and am waiting for them to get here.got sizes 72 and 74....I am on vacation next week and hope that I have alittle time to tinker with these....I have been thinking of replacing the intake...The one that is on it has a EGR valve do I have to put one back on it with a EGR port ? I tryed to bolt on a friends Edelbrock preformer carb and it would not work because it hits the EGR valve.None of my friends have cars that have a none computer controled quadrajet carbs on them to try.....


hope ta post good results soon

Cly

Well.....Jegs did a great job getting me the jets i orderd.....got them here next day at no extra charge http://www.camaros.net/forum/smile.gif.......So I installed the size 74 which looked alot smaller than the ones i drilled out.....Fired up the car and it does idle in park but ya drop it down in to drive and it stalls out....I think the jets fixed the rich condision at cruise speed but it is still lean at idle.......does anyone know where I can find pictures and disciption of the idle cercuit for a Q-jet????Maybe that would help me understand it alittle better....I am begining to think that the stock cam wasn't all that bad.....

Cly

I would try adjusting all the valves again with the engine running. Loosen each nut up until you hear the rocker start tapping. Then slowly tighten the nut until the rocker stops tapping, then go only 1/4 turn tighter.
Maybee I'm out in left field on this one, but if your lifter preload is too tight your intake valves won't be closing fully, and voila, no engine vacuum-poor idle-no fun.
Hey its free, try it.

HP Books, author Doug Roe. Book is "Rochester Carburetors".
Try at Amazon.com
Read up on the "idle feed restriction" those carbs were made very lean at idle and the idle screws were plugged so you can't adjust them.
They can be opened up by drilling from underneath, you need a socket to turn the mixture screws, but the idle feed restriction is ahead of the mixture screws, so if they can't richen up the idle enough, you probably need to drill them out slightly.
Make sure you don't have tight valves, or a vaccum leak, etc.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350
Can Am Vintage Racer